linux-kernel - [PATCH 2/2] PCI: iproc: add device shutdown for PCI RC

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Date:   Thu,  1 Jun 2017 10:57:51 +0530
From:   Oza Pawandeep <oza.oza@...adcom.com>
To:     Bjorn Helgaas <bhelgaas@...gle.com>, Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        Jon Mason <jonmason@...adcom.com>,
        bcm-kernel-feedback-list@...adcom.com,
        Oza Pawandeep <oza.oza@...adcom.com>,
        Andy Gospodarek <gospo@...adcom.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Oza Pawandeep <oza.pawandeep@...il.com>
Subject: [PATCH 2/2] PCI: iproc: add device shutdown for PCI RC

PERST# must be asserted around ~500ms before
the reboot is applied.

During soft reset (e.g., "reboot" from Linux) on some iProc based SoCs
LCPLL clock and PERST both goes off simultaneously.
This will cause certain Endpoints Intel NVMe not get detected, upon
next boot sequence.

This happens because; Endpoint is expecting the clock for some amount of
time after PERST is asserted, which is not happening in our case
(Compare to Intel X86 boards, will have clocks running).
this cause NVMe to behave in undefined way.

Essentially clock will remain alive for 500ms with PERST# = 0
before reboot.

This patch adds platform shutdown where it should be
called in device_shutdown while reboot command is issued.

So in sequence first Endpoint Shutdown (e.g. nvme_shutdown)
followed by RC shutdown is called, which issues safe PERST
assertion.

Signed-off-by: Oza Pawandeep <oza.oza@...adcom.com>
Reviewed-by: Ray Jui <ray.jui@...adcom.com>
Reviewed-by: Scott Branden <scott.branden@...adcom.com>

diff --git a/drivers/pci/host/pcie-iproc-platform.c b/drivers/pci/host/pcie-iproc-platform.c
index 90d2bdd..9512960 100644
--- a/drivers/pci/host/pcie-iproc-platform.c
+++ b/drivers/pci/host/pcie-iproc-platform.c
@@ -131,6 +131,13 @@ static int iproc_pcie_pltfm_remove(struct platform_device *pdev)
 	return iproc_pcie_remove(pcie);
 }
 
+static void iproc_pcie_pltfm_shutdown(struct platform_device *pdev)
+{
+	struct iproc_pcie *pcie = platform_get_drvdata(pdev);
+
+	iproc_pcie_shutdown(pcie);
+}
+
 static struct platform_driver iproc_pcie_pltfm_driver = {
 	.driver = {
 		.name = "iproc-pcie",
@@ -138,6 +145,7 @@ static int iproc_pcie_pltfm_remove(struct platform_device *pdev)
 	},
 	.probe = iproc_pcie_pltfm_probe,
 	.remove = iproc_pcie_pltfm_remove,
+	.shutdown = iproc_pcie_pltfm_shutdown,
 };
 module_platform_driver(iproc_pcie_pltfm_driver);
 
diff --git a/drivers/pci/host/pcie-iproc.c b/drivers/pci/host/pcie-iproc.c
index 05a3647..e9afc63 100644
--- a/drivers/pci/host/pcie-iproc.c
+++ b/drivers/pci/host/pcie-iproc.c
@@ -608,31 +608,38 @@ static int iproc_pcie_config_write32(struct pci_bus *bus, unsigned int devfn,
 	.write = iproc_pcie_config_write32,
 };
 
-static void iproc_pcie_reset(struct iproc_pcie *pcie)
+static void iproc_pcie_perst_ctrl(struct iproc_pcie *pcie, bool assert)
 {
 	u32 val;
 
 	/*
-	 * PAXC and the internal emulated endpoint device downstream should not
-	 * be reset.  If firmware has been loaded on the endpoint device at an
-	 * earlier boot stage, reset here causes issues.
+	 * The internal emulated endpoints (such as PAXC) device downstream
+	 * should not be reset. If firmware has been loaded on the endpoint
+	 * device at an earlier boot stage, reset here causes issues.
 	 */
 	if (pcie->ep_is_internal)
 		return;
 
-	/*
-	 * Select perst_b signal as reset source. Put the device into reset,
-	 * and then bring it out of reset
-	 */
-	val = iproc_pcie_read_reg(pcie, IPROC_PCIE_CLK_CTRL);
-	val &= ~EP_PERST_SOURCE_SELECT & ~EP_MODE_SURVIVE_PERST &
-		~RC_PCIE_RST_OUTPUT;
-	iproc_pcie_write_reg(pcie, IPROC_PCIE_CLK_CTRL, val);
-	udelay(250);
-
-	val |= RC_PCIE_RST_OUTPUT;
-	iproc_pcie_write_reg(pcie, IPROC_PCIE_CLK_CTRL, val);
-	msleep(100);
+	if (assert) {
+		val = iproc_pcie_read_reg(pcie, IPROC_PCIE_CLK_CTRL);
+		val &= ~EP_PERST_SOURCE_SELECT & ~EP_MODE_SURVIVE_PERST &
+			~RC_PCIE_RST_OUTPUT;
+		iproc_pcie_write_reg(pcie, IPROC_PCIE_CLK_CTRL, val);
+		udelay(250);
+	} else {
+		val = iproc_pcie_read_reg(pcie, IPROC_PCIE_CLK_CTRL);
+		val |= RC_PCIE_RST_OUTPUT;
+		iproc_pcie_write_reg(pcie, IPROC_PCIE_CLK_CTRL, val);
+		msleep(100);
+	}
+}
+
+int iproc_pcie_shutdown(struct iproc_pcie *pcie)
+{
+	iproc_pcie_perst_ctrl(pcie, true);
+	msleep(500);
+
+	return 0;
 }
 
 static int iproc_pcie_check_link(struct iproc_pcie *pcie, struct pci_bus *bus)
@@ -1310,7 +1317,8 @@ int iproc_pcie_setup(struct iproc_pcie *pcie, struct list_head *res)
 		goto err_exit_phy;
 	}
 
-	iproc_pcie_reset(pcie);
+	iproc_pcie_perst_ctrl(pcie, true);
+	iproc_pcie_perst_ctrl(pcie, false);
 
 	if (pcie->need_ob_cfg) {
 		ret = iproc_pcie_map_ranges(pcie, res);
diff --git a/drivers/pci/host/pcie-iproc.h b/drivers/pci/host/pcie-iproc.h
index 0bbe2ea..a6b55ce 100644
--- a/drivers/pci/host/pcie-iproc.h
+++ b/drivers/pci/host/pcie-iproc.h
@@ -110,6 +110,7 @@ struct iproc_pcie {
 
 int iproc_pcie_setup(struct iproc_pcie *pcie, struct list_head *res);
 int iproc_pcie_remove(struct iproc_pcie *pcie);
+int iproc_pcie_shutdown(struct iproc_pcie *pcie);
 
 #ifdef CONFIG_PCIE_IPROC_MSI
 int iproc_msi_init(struct iproc_pcie *pcie, struct device_node *node);
-- 
1.9.1